Re: linux-next: slab shrinkers: BUG at mm/list_lru.c:92

[Glauber Costa]

On Wed, Jun 19, 2013 at 09:13:46AM +0200, Michal Hocko wrote:
> On Tue 18-06-13 10:26:24, Glauber Costa wrote:
> [...]
> > Michal, would you mind testing the following patch?
> >
> > diff --git a/fs/inode.c b/fs/inode.c
> > index 00b804e..48eafa6 100644
> > --- a/fs/inode.c
> > +++ b/fs/inode.c
> > @@ -419,6 +419,8 @@ void inode_add_lru(struct inode *inode)
> >  
> >  static void inode_lru_list_del(struct inode *inode)
> >  {
> > +	if (inode->i_state & I_FREEING)
> > +		return;
> >  
> >  	if (list_lru_del(&inode->i_sb->s_inode_lru, &inode->i_lru))
> >  		this_cpu_dec(nr_unused);
> > @@ -609,8 +611,8 @@ void evict_inodes(struct super_block *sb)
> >  			continue;
> >  		}
> >  
> > -		inode->i_state |= I_FREEING;
> >  		inode_lru_list_del(inode);
> > +		inode->i_state |= I_FREEING;
> >  		spin_unlock(&inode->i_lock);
> >  		list_add(&inode->i_lru, &dispose);
> >  	}
> > @@ -653,8 +655,8 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty)
> >  			continue;
> >  		}
> >  
> > -		inode->i_state |= I_FREEING;
> >  		inode_lru_list_del(inode);
> > +		inode->i_state |= I_FREEING;
> >  		spin_unlock(&inode->i_lock);
> >  		list_add(&inode->i_lru, &dispose);
> >  	}
> > @@ -1381,9 +1383,8 @@ static void iput_final(struct inode *inode)
> >  		inode->i_state &= ~I_WILL_FREE;
> >  	}
> >  
> > +	inode_lru_list_del(inode);
> >  	inode->i_state |= I_FREEING;
> > -	if (!list_empty(&inode->i_lru))
> > -		inode_lru_list_del(inode);
> >  	spin_unlock(&inode->i_lock);
> >  
> >  	evict(inode);
> 
> No luck. I have this on top of inode_lru_isolate one but still can see
> hangs:
> 911 [<ffffffff8118325e>] __wait_on_freeing_inode+0x9e/0xc0
> [<ffffffff81183321>] find_inode_fast+0xa1/0xc0
> [<ffffffff8118529f>] iget_locked+0x4f/0x180
> [<ffffffff811efa23>] ext4_iget+0x33/0x9f0
> [<ffffffff811f6a5c>] ext4_lookup+0xbc/0x160
> [<ffffffff81174ad0>] lookup_real+0x20/0x60
> [<ffffffff81175254>] __lookup_hash+0x34/0x40
> [<ffffffff81179872>] path_lookupat+0x7a2/0x830
> [<ffffffff81179933>] filename_lookup+0x33/0xd0
> [<ffffffff8117ab0b>] user_path_at_empty+0x7b/0xb0
> [<ffffffff8117ab4c>] user_path_at+0xc/0x10
> [<ffffffff8116ff91>] vfs_fstatat+0x51/0xb0
> [<ffffffff81170116>] vfs_stat+0x16/0x20
> [<ffffffff8117013f>] sys_newstat+0x1f/0x50
> [<ffffffff81583129>] system_call_fastpath+0x16/0x1b
> [<ffffffffffffffff>] 0xffffffffffffffff
> 21409 [<ffffffff8118325e>] __wait_on_freeing_inode+0x9e/0xc0
> [<ffffffff81183321>] find_inode_fast+0xa1/0xc0
> [<ffffffff8118529f>] iget_locked+0x4f/0x180
> [<ffffffff811efa23>] ext4_iget+0x33/0x9f0
> [<ffffffff811f6a5c>] ext4_lookup+0xbc/0x160
> [<ffffffff81174ad0>] lookup_real+0x20/0x60
> [<ffffffff81177e25>] lookup_open+0x175/0x1d0
> [<ffffffff8117815e>] do_last+0x2de/0x780
> [<ffffffff8117ae9a>] path_openat+0xda/0x400
> [<ffffffff8117b303>] do_filp_open+0x43/0xa0
> [<ffffffff81168ee0>] do_sys_open+0x160/0x1e0
> [<ffffffff81168f9c>] sys_open+0x1c/0x20
> [<ffffffff81583129>] system_call_fastpath+0x16/0x1b
> [<ffffffffffffffff>] 0xffffffffffffffff
> 21745 [<ffffffff81179862>] path_lookupat+0x792/0x830
> [<ffffffff81179933>] filename_lookup+0x33/0xd0
> [<ffffffff8117ab0b>] user_path_at_empty+0x7b/0xb0
> [<ffffffff8117ab4c>] user_path_at+0xc/0x10
> [<ffffffff8116ff91>] vfs_fstatat+0x51/0xb0
> [<ffffffff81170116>] vfs_stat+0x16/0x20
> [<ffffffff8117013f>] sys_newstat+0x1f/0x50
> [<ffffffff81583129>] system_call_fastpath+0x16/0x1b
> [<ffffffffffffffff>] 0xffffffffffffffff
> 22032 [<ffffffff81179862>] path_lookupat+0x792/0x830
> [<ffffffff81179933>] filename_lookup+0x33/0xd0
> [<ffffffff8117ab0b>] user_path_at_empty+0x7b/0xb0
> [<ffffffff8117ab4c>] user_path_at+0xc/0x10
> [<ffffffff8116ff91>] vfs_fstatat+0x51/0xb0
> [<ffffffff81170116>] vfs_stat+0x16/0x20
> [<ffffffff8117013f>] sys_newstat+0x1f/0x50
> [<ffffffff81583129>] system_call_fastpath+0x16/0x1b
> [<ffffffffffffffff>] 0xffffffffffffffff
> 22621 [<ffffffff8118325e>] __wait_on_freeing_inode+0x9e/0xc0
> [<ffffffff81183321>] find_inode_fast+0xa1/0xc0
> [<ffffffff8118529f>] iget_locked+0x4f/0x180
> [<ffffffff811efa23>] ext4_iget+0x33/0x9f0
> [<ffffffff811f6a5c>] ext4_lookup+0xbc/0x160
> [<ffffffff81174ad0>] lookup_real+0x20/0x60
> [<ffffffff81177e25>] lookup_open+0x175/0x1d0
> [<ffffffff8117815e>] do_last+0x2de/0x780
> [<ffffffff8117ae9a>] path_openat+0xda/0x400
> [<ffffffff8117b303>] do_filp_open+0x43/0xa0
> [<ffffffff81168ee0>] do_sys_open+0x160/0x1e0
> [<ffffffff81168f9c>] sys_open+0x1c/0x20
> [<ffffffff81583129>] system_call_fastpath+0x16/0x1b
> [<ffffffffffffffff>] 0xffffffffffffffff
> 22711 [<ffffffff81178144>] do_last+0x2c4/0x780
> [<ffffffff8117ae9a>] path_openat+0xda/0x400
> [<ffffffff8117b303>] do_filp_open+0x43/0xa0
> [<ffffffff81168ee0>] do_sys_open+0x160/0x1e0
> [<ffffffff81168f9c>] sys_open+0x1c/0x20
> [<ffffffff81583129>] system_call_fastpath+0x16/0x1b
> [<ffffffffffffffff>] 0xffffffffffffffff
> 22946 [<ffffffff81178144>] do_last+0x2c4/0x780
> [<ffffffff8117ae9a>] path_openat+0xda/0x400
> [<ffffffff8117b303>] do_filp_open+0x43/0xa0
> [<ffffffff81168ee0>] do_sys_open+0x160/0x1e0
> [<ffffffff81168f9c>] sys_open+0x1c/0x20
> [<ffffffff81583129>] system_call_fastpath+0x16/0x1b
> [<ffffffffffffffff>] 0xffffffffffffffff
> 23393 [<ffffffff81178144>] do_last+0x2c4/0x780
> [<ffffffff8117ae9a>] path_openat+0xda/0x400
> [<ffffffff8117b303>] do_filp_open+0x43/0xa0
> [<ffffffff81168ee0>] do_sys_open+0x160/0x1e0
> [<ffffffff81168f9c>] sys_open+0x1c/0x20
> [<ffffffff81583129>] system_call_fastpath+0x16/0x1b
> [<ffffffffffffffff>] 0xffffffffffffffff
> -- 
Sorry if you said that before Michal.

But given the backtrace, are you sure this is LRU-related? You mentioned you bisected
it but found nothing conclusive. I will keep looking but maybe this could benefit from
a broader fs look

In any case, the patch we suggested is obviously correct and we should apply nevertheless.
I will write it down and send it to Andrew.
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